The invention relates to a circular knitting machine comprising at least one carrier in which knitting implements are displaceably mounted, a cam arrangement for controlling the knitting implements and a heat exchange apparatus for the carrier and the cam arrangement. The invention also relates to a method of providing uniform temperature conditions on a circulat knitting machine of the above mentioned type.
In circular knitting machines with large numbers of systems and high speeds of rotation, in particular large-scale circular knitting machines with diameters of 30 inches and with a high output, very high temperatures of up to about 150.degree. Celsius may occur due to the friction between the knitting implements (needles, pressers, sinkers or the like) in the grooves of the carriers (needle cylinder, rib plates, sinker ring or the like) or between the knitting implements and the cam arrangements (cylinder cams, rib cams, sinker cams or the like). A consequence of that is that those components can no longer be touched and any necessary repairs, for example the replacement of a broken needle, can only be carried out when special safety precautions are taken or after the circular knitting machine has adequately cooled down.
Apart from that, circular knitting machines which run hot are frequently found to suffer from operational disturbances, for example pattern errors or variations in the stitch length or the yarn tension, which do not occur when the machines are cold or operating only slowly, even if the circular knitting machine were set in the optimum fashion at ambient temperature. Those operational distrubances must therefore be attributed to the influences of temperature and the fact that varying operating temperatures have a detrimental influence on the operational reliability of a circular knitting machine.
Attempts have already been made to counteract operational disturbances of that kind by means of structural variations in certain parts of the machine, for example the needle cylinder (see German laid-open application (DE-OS) No. 33 16 382). Hitherto however there is no known manner of procedure which could be used to deal with all operational distrubances which must be attributed to temperature influences.
Accordingly generally the use of heat exchange apparatuses is considered as the only possible way of effectively providing remedies in this respect. The heat exchange apparatuses may include for example blowing nozzles by means of which gaseous heat exchange agents, in particular air, are blown from the outside or the inside on to the carriers of the knitting implements and/or the cam arrangements (German utility model No. 76 38 042 and German laid-open applications (DE-OS) Nos. 16 35 836 and 31 01 154) or cooling circuits which are formed in the carriers and through which a liquid coolant, in particular oil, is passed (German patent specification No. 1 635 931 and German laid-open application (DE-OS) No. 22 00 154). It is also known that oil lubricating systems and fuzz blow-off device which are provided on circular knitting machines for other reasons inevitably also have a certain cooling effect. Finally it is known that, in the event of a cold start, circular knitting machines have a tendency to malfunction and it is therefore desirable for them firstly to be allowed to warm up at a low speed before being switched over to their nominal speed of rotation.
The previously known heat exchange apparatuses of that kind are all based on the assumption that more or less uncontrolled temperature adjustment (cooling or heating) of the parts of a circular knitting machine which heat up the fastest and to the greatest extent, for example the needle cylinder, is already sufficient in order to solve all problems which occur in that context. However that assumption has proven to be false in practice. On the contrary, the use of the known heat exchange apparatuses can even result in greater operational disturbances than when such apparatuses are not employed.